Method of forming material using atomic layer deposition and method of forming capacitor of semiconductor device using the same

ABSTRACT

Disclosed are methods of forming dielectric materials using atomic layer deposition (ALD) and methods of forming dielectric layers from such materials on a semiconductor device. The ALD process utilizes a first reactant containing at least one alkoxide group that is chemisorbed onto a surface of a substrate and then reacted with an activated oxidant that contains no hydroxyl group to form a dielectric material exhibiting excellent step coverage and improved leakage current characteristics.

PRIORITY STATEMENT

This is a Divisional Application of application Ser. No. 10/615,881,filed Jul. 10, 2003 now U.S. Pat. No. 7,087,482, which is an U.S.nonprovisional patent application claiming priority under 35 U.S.C. §119 to Korean Application Nos. 2001-3165, filed on Jan. 19, 2001, and2002-42217, filed on Jul. 18, 2002, and claiming priority under 35U.S.C. § 120 to U.S. application Ser. No. 10/047,706, filed Jan. 15,2002, the contents of each of these applications also being herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing semiconductordevices, and more particularly, to a method of forming a material layerduring the manufacture of semiconductor devices using the technique ofatomic layer deposition (ALD) and a method of forming the dielectriclayer of a capacitor of a semiconductor device using ALD.

2. Description of the Related Art

The decrease in cell capacitance resulting from a reduction in availablememory cell area makes it difficult to increase the integration densityof semiconductor memory devices. Decreased cell capacitance degrades thedata readability from memory cells, increases the soft error rate andalso hinders low-voltage operation of the semiconductor memory devices.

Several techniques have been utilized to maintain or increase the cellcapacitance without significantly increasing the wafer area occupied bythe memory cell. Two such methods of increasing capacitance within alimited cell area including thinning the dielectric layer of thecapacitor and/or increasing the effective surface area of the capacitorlower electrode using a cylindrical or pin-shaped structure. However,for memory devices such as dynamic random access memories (DRAMs) havingcapacities of 1 gigabit or more, it is difficult to obtain sufficientcapacitance to ensure satisfactory operation of the memory devices witheither of the methods noted above.

To further increase the capacitance that can be achieved within a givenmemory cell size, research efforts have been directed toward the use ofmaterials having a higher dielectric constant (κ), such as Ta₂O₅, Y₂O₃,HfO₂, ZrO₂, Nb₂O₅, BaTiO₃ or SrTiO₃, as the dielectric layer of acapacitor is being actively conducted.

Conventionally, a Ta₂O₅ film has been widely used because of itsrelatively high dielectric constant and high thermal stability. However,the use of the Ta₂O₅ film has a potential problem in that it typicallyis highly reactive with a polysilicon film. If the lower electrode ofcapacitor is formed from polysilicon, oxygen (O) from the Ta₂O₅ film canreact with silicon of the polysilicon layer during the formation of theTa₂O₅ film or during a subsequent thermal treatment after the Ta₂O₅ filmhas been formed to from silicon dioxide at the surface of thepolysilicon layer. Further, oxygen vacancies within Ta₂O₅ film mayincrease leakage current.

In an attempt to address this problem, lower electrodes have been formedfrom materials that are believed to be relatively more difficult tooxidize than polysilicon. Examples of such materials include noblemetals such as platinum (Pt), ruthenium (Ru) and iridium (Ir) orconductive metal nitride films such as titanium nitride (TiN). However,the use of a noble metal or a metal nitride presents other potentialproblems.

A conventional tantalum oxide (Ta₂O₅) film is typically formed bychemical vapor deposition (CVD) in an oxygen atmosphere usingpentaethoxide tantalum (PET), Ta(OCH₃)₅ or TaCl₅ as a tantalum sourcegas and oxygen (O₂), water (H₂O), hydrogen peroxide (H₂O₂) or nitrousoxide (N₂O) as an oxygen source gas. Notwithstanding any advantagesassociated therewith, a composition of these source gases oftennegatively impacts the coverage of the Ta₂O₅ film, presumably due to theoxidation of the lower electrode. For example, if ruthenium (Ru) is usedas a lower electrode, the surface of the Ru layer can be oxidized toform a RuO₂ film that minimizes or prevents the formation of the desiredTa₂O₅ film. This problem often occurs when a Ta₂O₅ film is used as adielectric layer in a cylindrical or concave-shaped capacitor having alarge aspect ratio. In such an instance, the Ta₂O₅ film will tend to bemore thinly deposited or largely missing from the portion of the Ruelectrode in the lower portion of a cylindrical opening, while the Ta₂O₅film is thickly deposited on the upper portion of the opening, therebyresulting in poor step coverage of the resulting Ta₂O₅ film.

Generally, thin films such as dielectric films are formed usingdeposition methods such as CVD, low-pressure chemical vapor deposition(LPCVD), plasma-enhanced chemical vapor deposition (PECVD) and/orsputtering. The step coverage that is typically obtained with CVD-basedmethods, however, remained less then desired. Accordingly, atomic layerdeposition (ALD) processes have been proposed as an alternative toCVD-based deposition methods because the ALD processes can be performedat lower temperatures while exhibiting improved step coverage.

One such ALD process technology is disclosed in U.S. Pat. No. 6,124,158,in which a first reactant is introduced to react with the treatedsurface to form a bonded monolayer of reactive species. A secondreactant is then introduced to react with the bonded monolayer to form athin layer of the desired material on the treated surface. After eachstep in the cycle, the reaction chamber is purged with an inert gas toprevent reaction except at the treated surface.

Since an ALD film has low thermal budget, excellent step coverage, andexcellent thickness control and uniformity, efforts have been made todevelop methods whereby a metal oxide such as Ta₂O₅, Y₂O₃, HfO₂, ZrO₂,or Nb₂O₅, may be deposited using an ALD method to form the high-κdielectric layer of a capacitor. One such effort formed a metal oxide byALD using as the metal precursor a halide such as HfCl₄ in combinationwith an oxidant such as O₂, H₂O, H₂O₂ or N₂O. However, efforts offorming such thin films using halide group precursors tend to result inunsatisfactory levels of step coverage.

Further, when H₂O is used as the oxidant, hydrogen (H) radicals tend toreact with halogen ligands separated from HfCl₄ to thereby form a gasincluding hydrochloric acid (HCl). Because the HCl gas tends to etch thethin film on the semiconductor device, the surface morphology of theresulting thin film is compromised. In addition, the metal may combinewith the —H and/or —OH groups formed, resulting in the incorporation ofundesirable impurities, e.g., metal hydroxides, into the metal oxidefilm. If a metal oxide film containing impurities such as metalhydroxides is utilized as a dielectric layer in a semiconductor device,the metal hydroxides may act as trap sites or a current leakage sites,thereby degrading the dielectric characteristics of the resultingdevice.

SUMMARY OF THE INVENTION

In an exemplary embodiment, the present invention provides a method offorming a material using atomic layer deposition (ALD) having improvedstep coverage and leakage current preventing characteristics.

In an exemplary embodiment, the present invention provides a method offorming a semiconductor capacitor having a large aspect ratio in whichoxidization of the lower electrode is suppressed in order to form ametal oxide thin film having improved uniformity

In an exemplary embodiment, the present invention provides a method offorming a material utilizing an ALD process comprising the steps of: (a)introducing a first reactant containing a first atom necessary to formthe material and at least one alkoxide group on a substrate; (b)chemisorbing a portion of the first reactant onto the substrate; (c)introducing a second reactant that is activated and does not contain ahydroxyl group to the substrate; and (d) chemically reacting the secondreactant with the chemisorbed first reactant to form an atomic layer ofthe material on the substrate.

In an exemplary embodiment, the atomic layer formed on the substrate canserve as a dielectric layer of a capacitor for a semiconductor device oras a gate dielectric layer for a semiconductor device.

In an exemplary embodiment, the present invention provides a method offorming a thin film using an ALD process comprising the steps of: (a)placing a substrate into a chamber; (b) introducing a first reactantincluding a metal alkoxide into the chamber; (c) chemisorbing a portionof the first reactant onto the substrate; (d) removing non-chemicallyadsorbed first reactant from the chamber; (e) introducing a secondreactant as an activated oxidant that lacks a hydroxyl group into thechamber; (f) chemically reacting the second reactant with thechemisorbed first reactant to form an atomic layer of a metal oxide filmon the substrate; and (g) removing the non-chemically reacted secondreactant from the chamber.

In an exemplary embodiment, the present invention provides a method offorming a capacitor comprising the steps of: (a) forming a firstelectrode on a semiconductor substrate; (b) introducing a first reactantcontaining a first atom for forming a dielectric material and at leastone alkoxide group on the first electrode; (c) chemisorbing a portion ofthe first reactant onto the first electrode; (d) introducing a secondreactant containing no hydroxyl group on the first electrode; (e)chemically reacting the second reactant with the chemisorbed firstreactant to form a dielectric layer on the first electrode; and (f)forming a second electrode on the dielectric layer.

According to an exemplary embodiment, the present invention involves anALD process in which a metal alkoxide precursor and an oxidant thatcontains no hydroxyl group may be reacted to form a thin film havingimproved step coverage and an improved leakage current characteristics.When such a thin film is used as the capacitor dielectric layer or asthe gate dielectric layer in a semiconductor device, the reliability ofthe resulting semiconductor device may also be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will become apparent byreference to the following detailed description when considered inconjunction with the accompanying drawings wherein:

FIGS. 1A to 1E are cross-sectional views illustrating a method offorming a material using atomic layer deposition according to anexemplary embodiment of the present invention;

FIG. 2 is a graph showing a deposition rate of hafnium oxide (HfO₂) filmversus the deposition temperature in accordance with an exemplaryembodiment of the present invention;

FIG. 3 is a graph showing a thickness of HfO₂ film versus the depositioncycle in accordance with an exemplary embodiment of the presentinvention;

FIGS. 4A and 4B are graphs showing the binding status of HfO₂ film as afunction of post annealing and deposition temperature respectively inaccordance with an exemplary embodiment of the present invention;

FIG. 5 is a graph showing a depth profile of a HfO₂ film formedaccording to an exemplary embodiment of the present invention;

FIGS. 6A to 6E are cross-sectional views illustrating a method ofmanufacturing a semiconductor device in accordance with an exemplaryembodiment of the present invention;

FIG. 7 is a graph showing the leakage current of a capacitormanufactured according to an exemplary embodiment of the presentinvention;

FIG. 8 is a cross-sectional view of a cylinder type capacitor inaccordance with an exemplary embodiment of the present invention;

FIGS. 9A and 9B are schematic views showing a cross-section of asubstrate photographed by scanning electron microscope (SEM), in casethat a Ta₂O₅ films are formed using H₂O and O₂ as an oxygen source,respectively in accordance with an exemplary embodiment of the presentinvention;

FIG. 10 is a graph showing equilibrium vapor pressures of PET andTAT-DMAE precursors versus temperature in accordance with an exemplaryembodiment of the present invention; and

FIG. 11 is a cross-sectional view schematically illustrating anadsorption mechanism of gaseous tantalum precursors on a Ru lowerelectrode in accordance with an exemplary embodiment of the presentinvention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. In thefollowing drawings, the same numerals are used to indicate the same orcorresponding elements.

FIGS. 1A to 1E are cross-sectional views illustrating a method offorming a material using atomic layer deposition according to anexemplary embodiment of the present invention.

Referring to FIG. 1A, a substrate 1 including a semiconductor materialsuch as silicon (Si) is placed into a deposition chamber (not shown). Afirst reactant 2 containing a first atom (e.g., a metal or a semimetal)necessary to produce the desired material and at least one alkoxidegroup as a ligand is then introduced into the chamber. In an exemplaryembodiment, the first reactant 2 is a metal alkoxide. The metal alkoxidemay include a second group metal alkoxide including at least one secondgroup metal such as magnesium (Mg), calcium (Ca) or strontium (Sr), athird group metal alkoxide including at least one third group metal suchas boron (B), aluminum (Al) or lanthanum (La) (even though boron isconsidered a semimetal), a fourth group metal alkoxide including atleast one fourth group metal such as titanium (Ti), zirconium (Zr),hafnium (Hf), silicon (Si), germanium (Ge), tin (Sn) or lead (Pb) (eventhough silicon and germanium are more commonly considered semimetals)and a fifth group metal alkoxide including at least one fifth groupmetal such as vanadium (V), niobium (Nb), tantalum (Ta), phosphorus (P),arsenic (As) or antimony (Sb) (even though P is not generally considereda metal and As and Sb are more commonly considered semimetals). In anexemplary embodiment of the present invention, the metal alkoxide is afourth group metal alkoxide.

An example of a Mg alkoxide is Mg[OC₂H₄OCH₃]₂, an example of a Caalkoxide is Ca[OC₂H₄OCH₃]₂, and an example of a Sr alkoxide isSr[OC₂H₄OCH₃]₂. Examples of B alkoxides include B[OCH₃]₃, B[OC₂H₅]₃,B[OC₃H₇]₃ and B[OC₄H₉]₃, examples of Al alkoxides includeAl[OC₂H₄OCH₃]₂, Al[OCH₃]₃, Al[OC₂H₅]₃, Al[OC₃H₇]₃ and Al[OC₄H₉]₃, andexamples of La alkoxides include La[OC₂H₄OCH₃]₂ and La[OC₃H₇CH₂OC₃H₇]₃.

Examples of Ti alkoxides include Ti[OCH₃]₄, Ti[OC₃H₇]₄, Ti[OC₄H₉]₄ andTi[OC₂H₅]₂[OC₂H₄N(CH₃)₂]₂, examples of Zr alkoxides include Zr[OC₃H₇]₄,Zr[OC₄H₉]₄ and Zr[OC₄H₈OCH₃]₄, examples of Hf alkoxides includeHf[OC₄H₉]₄, Hf[OC₄H₈OCH₃]₄, Hf[OC₄H₉]₂[OC₂H₄N(CH₃)₂]₂,Hf[OC₄H₉]₂[OC₄H₈OCH₃]₂, Hf[OSi(C₂H₅)₃]₄, Hf[OC₂H₅]₄, Hf[OC₃H₇]₄,Hf[OC₄H₉]₄ and Hf[OC₅H₁₁]₄. Examples of Si alkoxides include Si[OCH₃]₄,Si[OC₂H₅]₄, Si[OC₃H₇]₄, HSi[OCH₃]₃, HSi[OC₂H₅]₃, Si[OCH₃]₃F,Si[OC₂H₅]₃F, Si[OC₃H₇]₃F and Si[OC₄H₉]₃F, examples of Ge alkoxidesinclude Ge[OCH₃]₄, Ge[OC₂H₅]₄, Ge[OC₃H₇]₄ and Ge[OC₄H₉]₄, examples of anSn alkoxide include Sn[OC₄H₉]₄ and Sn[OC₃H₇]₃[C₄H₉], and examples of Pbalkoxides include Pb[OC₄H₉]₄ and Pb₄O[OC₄H₉]₄.

Examples of V alkoxides include VO[OC₂H₅]₃ and VO[OC₃H₇]₃, examples ofNb alkoxides include Nb[OCH₃]₅, Nb[OC₂H₅]₅, Nb[OC₃H₇]₅ and Nb[OC₄H₉]₅,examples of Ta alkoxides include Ta[OCH₃]₅, Ta[OC₂H₅]₅, Ta[OC₃H₇]₅,Ta[OC₄H₉]₅, Ta[OC₂H₅]₄[OC₂H₄N(CH₃)₂] and Ta[OC₂H₅]₄[CH₃COCHCOCH₃],examples of P alkoxides include P[OCH₃]₃, P[OC₂H₅]₃, P[OC₃H₇]₃,P[OC₄H₉]₃, PO[OC₂H₅]₃, PO[OC₃H₇]₃ and PO[OC₄H₉]₃, examples of Asalkoxides include As[OCH₃]₃, As[OC₂H₅]₃, As[OC₃H₇]₃ and As[OC₄H₉]₃, andexamples of Sb alkoxides include Sb[OC₂H₅]₃, Sb[OC₃H₇]₃ and Sb[OC₄H₉]₃.

Referring to FIG. 1B, during the step of introducing the first reactant2, a first portion of the first reactant 2 chemisorbs and forms a layer4 on the surface of the substrate 1. A second portion of the firstreactant 2 is physically attached (physisorbed) onto and is loosely heldto the chemisorbed layer 4 of the first reactant 2. The chamber may thenbe purged with an inert gas such as argon (Ar) or nitrogen (N₂), andvacuum purged to remove the non-chemically absorbed portions of thefirst reactant 2 from the chamber, leaving the chemisorbed layer 4 ofthe first reactant 2 intact on the substrate 1.

Referring to FIG. 1C, a second reactant 6 comprising an activatedoxidant that does not contain a hydroxyl group is introduced into thechamber to chemically react the second reactant 6 with the chemisorbedfirst reactant 2, and thereby form an atomic layer 8 of the desiredmaterial on the substrate 1. The non-chemically reacted portion of thesecond reactant is then removed from the chamber. That is, the firstatom (metal or non-metal) from the chemisorbed first reactant 2 reactswith oxygen of the second reactant 6 to form a metal oxide film as theunit of atomic layer. The second reactant 6 is an activated oxidant thatcan form oxygen (O) radicals and may be ozone (O₃), plasma O₂, remoteplasma O₂ or plasma N₂O. When an oxygen gas is treated with an O₃generator, a portion of O₂ gas is converted into O₃, thereby producing amixed gas comprising O₂ and O₃ with the O₃ gas typically present in amole percent of about 5 to 15%.

Referring to FIG. 1D, the chamber is then purged with an inert gas suchas Ar or N₂, and then vacuum purged, to remove the non-chemicallyreacted portions of the second reactant 6 from the chamber.

The steps of introducing the first reactant, purging the first reactant,introducing the second reactant and purging the second reactant can berepeated to achieve any desired thickness of material layer 8 a. Thematerial layer 8 a is an insulating layer, and may be a metal oxidelayer including a metal oxide such as HfO₂, ZrO₂, Ta₂O₅, Y₂O₃, Nb₂O₅,TiO₂, CeO₂, In₂O₃, RuO₂, MgO, Sro, B₂O₃, SiO₂, GeO₂, SnO₂, PbO, PbO₂,V₂O₃, La₂O₃, As₂O₅, As₂O₃, Pr₂O₃, Sb₂O₃, Sb₂O₅, CaO or P₂O₅.

Since metal alkoxides known as precursors for CVD processes tend todecompose at a higher temperatures, ALD processes using the metalalkoxide may be carried out at a temperature of between about 100 and500° C., and may typically be carried out at a temperature of less thanabout 400° C. Metal alkoxides tend to have higher vapor pressures thanthat of other precursors, e.g., halide precursors under similar processconditions. A higher vapor pressure indicates that there are arelatively larger number of gas molecules when compared to a systemhaving a lower vapor pressure. With respect to the metal alkoxides, theamount of metal source gas provided to the deposition chamber isrelatively large, thus increasing the relative number of molecules madeavailable for reaction at the bottom of the stepped region. Therefore,the metal alkoxide and other alkoxides employed as precursors inaccordance with the exemplary embodiments of the present invention canform a thin film exhibiting improved step coverage when compared withconventional precursors.

In an exemplary embodiment, a thin film is formed using an ALD methodusing precursors of an alkoxide group, e.g., a tetra-butoxy-hafnium[Hf(OtBu)₄], and oxygen (O₂) gas may be formed with a lower thermalbudget than a conventional CVD-HfO₂ film that would typically bedeposited at a higher temperature of about 500° C. or more, therebycausing a higher thermal budget. Further, the ALD-HfO₂ film thicknessmay be controlled to a thickness of 20 Å or less, in comparison with theCVD-HfO₂ film that will typically be deposited to a thickness of atleast several tens of Angstroms.

Ozone (O₃) gas used as an activated oxidant can oxidize a metal whilegenerating no, or substantially no, by-products when compared withconventional oxidants. According to exemplary embodiments of the presentinvention, a second reactant that does not contain a hydroxyl group maybe utilized to suppress the formation of undesirable impurities such asa metal-OH bond, thereby producing a thin film having improvedstoichiometry and dielectric properties.

Hereinafter, a method of forming a HfO₂ film to act as the capacitordielectric layer or gate dielectric layer using ALD process inaccordance with an exemplary embodiment of the present invention will bedescribed.

A substrate such as a silicon wafer is placed in a chamber thatmaintains a temperature of about 300° C. and the chamber is evacuated toa pressure of about 0.4 Torr. Using an inert carrier gas such as argon(Ar) or nitrogen (N₂), a flow of 200 sccm of a first reactant containinga first atom necessary for forming the desired dielectric film, i.e.,hafnium, and an alkoxide group may be introduced into the chamber (onthe substrate) for about 1 second. Although as the first reactant, oneor more hafnium alkoxides such as Hf(OEt)₄, Hf(OPr)₃,Hf(OBu)₄[Hf(OnBu)₄, Hf(OtBu)₄], Hf(mmp)₄, Hf(OtBu)₂(dmae)₂,Hf(OtBu)₂(mmp)₂ or Hf[OSi(C₂H₅)₄ may be used, Hf(OtBu)₄ was utilized inthe exemplary embodiment described further below.

In the shorthand notation used above, “Et” denotes an ethyl group, “Pr”denotes a prophyl group, “nBu” denotes an n-butyl group, “tBu” denotes at-butyl group, “dmae” denotes a dimethyaminoethoxide group(—OC₂H₄N(CH₃)₂) and “mmp” denotes a 1-methoxy-2-methyl-2-propoxy group(—OC₄H₈OCH₃).

During the introduction of the first reactant, a first portion of theHf(OtBu)₄ chemisorbs and forms a layer on the surface of the substrate.A second portion of Hf(OtBu)₄ physically attaches (physisorbs) onto andis loosely held to the chemisorbed layer of Hf(OtBu)₄. Hf(OtBu)₄ is aliquid at a room temperature, may be represented by Formula I asillustrated below, and has a vapor pressure of 0.5 Torr at a temperatureof 50.3° C.

The chamber (substantially, the upper portion of the substrate) ispurged with an inert gas such as Ar or N₂ and vacuum purged. During thepurging steps, the non-chemically absorbed portions of Hf(OtBu)₄ areremoved from the chamber while the chemisorbed layer of Hf(OtBu)₄remains intact on the substrate.

A flow of 200 sccm of a second reactant comprising an activated oxidantcontaining no hydroxyl group, such as O₃, plasma O₂, remote plasma O₂ orplasma N₂O, is then introduced into the chamber for about 2 seconds.This allows an activated oxygen (O) from the second reactant to reactwith the chemisorbed Hf(OtBu)₄ on the substrate to form a HfO₂ film asan atomic layer on the substrate.

The chamber is then purged with an inert gas such as Ar or N₂ and then,vacuum purged to remove substantially all of the non-chemically reactedsecond reactant from the chamber. The steps of introducing Hf(OtBu)₄into the chamber, purging the chamber, introducing the activated oxidantinto the chamber and purging the chamber can be repeated as necessary toachieve any desired thickness of the resulting HfO₂ film. During thesesteps, in an exemplary embodiment, the temperature of the chamber ismaintained at a temperature below about 400° C., such as a temperatureof about 300° C.

According to exemplary embodiments of the present invention, hafniumalkoxide precursors such as Hf(OtBu)₄, which have a higher vaporpressure than other precursors such as hafnium halides such as HfCl₄,may be used to form a HfO₂ film with improved step coverage. Further, byusing an activated oxidant that contains no hydroxyl group the formationof impurities in which a hafnium (Hf) bonds with —H or —OH may besuppressed or eliminated, thereby obtaining a HfO₂ film having improvedstoichiometry that contains few or no impurities that could act aselectron trap sites or current leakage sites.

After depositing the HfO₂ film with an ALD process using Hf(OtBu)₄ andO₃ as described above, various characteristics of the HfO₂ film wereobserved through the following experiments. In exemplary embodiments,the dosing step, Ar purging step, O₃ dosing step and Ar purging stepwere carried out for one second, two seconds, two seconds and twoseconds, respectively. The ALD process was also performed at variousexemplary deposition temperatures including 250° C., 300° C., 350° C.and 400° C.

FIG. 2 is a graph showing a deposition rate of HfO₂ film versus thedeposition temperature. In the graph, the horizontal axis represents thedeposition temperature (° C.) and the vertical axis represents thedeposition rate (Å/cycle). As reflected in FIG. 2, the deposition rateof HfO₂ film was at a minimum at the deposition temperature of about300° C. and increased at a temperature of about 400° C. Accordingly, theHfO₂ film exhibits stronger ALD characteristics when deposited at atemperature of in the vicinity of 300° C., while the properties of thefilm deposited at 400° C. or more begins to resemble those of aCVD-deposited film. Therefore, in an exemplary embodiment the HfO₂ filmis deposited at a temperature of 400° C. or less, and in anotherexemplary embodiment, 250 to 350° C.

FIG. 3 is a graph showing a thickness of HfO₂ film versus the depositioncycle. In the graph, the horizontal axis represents the deposition cycleand the vertical axis represents the film thickness. The depositionprocess was performed at a temperature of 300° C.

Referring to FIG. 3, since the HfO₂ film has ALD characteristics in thevicinity of 300° C., the thickness of HfO₂ film linearly increased inaccordance with the deposition cycle. Accordingly, the HfO₂ filmdeposited by an ALD process using Hf(OtBu)₄ and O₃ exhibits improvedthickness control and uniformity, thereby decreasing pattern loadingeffects. Further, for HfO₂ films deposited by an ALD process usingHf(OtBu)₄ and O₃, exhibited step coverage (the thickness ratio of thefilm formed on the upper portion of the structure to film formed on thelower portion of the structure) of about 80% or more on a structurehaving an aspect ratio of more than about 13:1.

FIG. 4A is a graph showing the binding status of oxygen examined throughan X-ray photoelectric spectroscopy (XPS) analysis of as-deposited andpost-annealed HfO₂ film. In FIG. 4A, a trace (a) indicates the bindingstatus of as-deposited HfO₂ film, and a trace (b) indicates the bindingstatus of post-annealed HfO₂ film. In the graph, the horizontal axisrepresents a binding energy (eV) and the vertical axis representsintensity.

Referring to FIG. 4A, a number of C—O bonds was detected in theas-deposited HfO₂ film. However, the C—O bonds within HfO₂ film nearlyvanished and the Hf—O binding energy was shifted in the oppositedirection of Hf metal phase after post-annealing. Accordingly, thebinding status within the HfOx film was stabilized by thepost-annealing.

FIG. 4B is a graph showing the binding status of Hf examined through anXPS analysis of post-annealed HfO₂ film after the deposition of HfO₂film was carried out at various temperatures. In FIG. 4B, the horizontalaxis represents a binding energy (eV) and the vertical axis representsintensity. As reflected in FIG. 4B, the binding status of HfO₂ filmappeared to be most stable for films formed at the depositiontemperature of about 350° C.

FIG. 5 is a graph showing a depth profile of HfO₂ film in accordancewith an exemplary embodiment of the present invention. The depth profilewas observed by a time of flight-secondary ion-mass spectrometer(TOF-SIMS). In the graph, the horizontal axis represents time (seconds)and the vertical axis represents intensity. As reflected in FIG. 5, Hf—Obonds were uniformly detected in the HfO₂ film through the substantiallyfull thickness of the HfO₂ film, confirming the formation of a generallyuniform HfO₂ film that contains no significantly impurities such asHf(OH)₂ that could act as electron trap sites or current leakage sites.

Exemplary Method of Manufacturing a Semiconductor Device

FIGS. 6A to 6E are cross-sectional views illustrating a method ofmanufacturing a semiconductor device in accordance with an exemplaryembodiment of the present invention. Referring to FIG. 6A, asemiconductor substrate 100 is divided into an active region 101 and anisolation region (or field region) 102 on which are formed transistorsincluding a gate dielectric layer 104, a gate electrode 110, andsource/drain regions 116 a and 116 b. Since a very thin gate dielectriclayer of about 10 Å is needed in a semiconductor memory device having acapacity of 1 gigabit or more, the gate dielectric layer 104 may beformed using an exemplary embodiment of the present invention.Specifically, as shown in FIGS. 1A to 1E, an ALD process using metalalkoxide precursors and an activated oxidant such as O₃, plasma O₂,remote plasma O₂ or plasma N₂O, may be utilized to form the gatedielectric layer 104 from a metal oxide film. In an exemplaryembodiment, the gate dielectric layer 104 of HfO₂ is formed by an ALDprocess using Hf(OtBu)₄ and O₃.

In an exemplary embodiment, the gate electrode 110 may have a polycidestructure including an impurity-doped polysilicon layer and a metalsilicide layer stacked thereon. A capping insulating layer 112 andsidewall spacers 114 are formed on the top and side of the gateelectrode 110, respectively. In an exemplary embodiment, the cappinginsulating layer 112 and sidewall spacers 114 may be formed from asilicon oxide, a silicon nitride or other suitable insulating material.

Referring to FIG. 6B, a first insulating layer 118 comprising an oxideis formed on the entire surface of the substrate 100 on which thetransistors are formed. Then, a portion of the first insulating layer118 is etched away through a photolithography process to thereby form acontact hole 120 to partially expose the source region 116 a.

A first conductive layer, e.g., a P-doped polysilicon layer, isdeposited on the contact hole 120 and the first insulating layer 118.Through an etch-back process or chemical-mechanical polishing (CMP)process, the first conductive layer is removed until the surface of thefirst insulating layer 118 is exposed, thereby forming a contact plug122 in the contact hole 120.

Referring to FIG. 6C, an etch stopping layer 123 is formed on thecontact plug 122 and the first insulating layer 118. The etch stop layer123 comprises a material having a high etch selectivity with respect tothe first insulating layer 118, for example, silicon nitride(Si_(x)N_(y)) or silicon oxynitride (SiON) (that is, the etch rate ofthe first insulating layer 118 is much higher than the etch rate of theetch stopping layer 123 under similar etch conditions).

After forming a second insulating layer 124 comprising an oxide on theetch stop layer 123, a portion of the second insulating layer 124 and aportion of the etch stop layer 123 are etched away to form an opening126 that exposes a surface of the contact plug 122. Specifically, afteretching the second insulating layer 124 until the etch stopping layer123 is exposed, an over-etching process is carried out for a desiredtime to complete opening 126 and expose a surface of the contact plug122 and an adjacent portion of the first insulating layer 118. Theopening 126 may be formed with a non-vertical sidewall slope such thatthe inlet of the opening 126 is wider than the bottom thereof. This isbecause the etch rate of the bottom of the opening 126 is decreasedrelative to the etch rate at the inlet of the opening 126 due to loadingeffects during the etching process.

A second conductive layer 127 is deposited on the side and bottom of theopening 126 and the top of the second insulating layer 124. In anexemplary embodiment, the second conductive layer 127 may comprise asemiconductor material such as polysilicon, noble metals such as Ru, Pt,Ir or a combination thereof, or a conductive metal nitride such as TiN,TaN, WN or a combination thereof.

Referring to FIG. 6D, after forming a sacrificial layer (not shown) onthe second conductive layer 127 and the opening 126, the upper portionof the sacrificial layer is etched back or otherwise removed such thatthe only remaining portion of the second conductive layer 127 is foundon the side and bottom of the opening 126. By doing so, the secondconductive layer 127 deposited on the surface of the second insulatinglayer 124 is removed to separate the second conductive layer 127deposited along the profile of the opening 126 into a cell unit. Thesacrificial layer is then removed to form a lower electrode 128 of acapacitor on each of the memory cell regions. The lower electrode 128has a generally tapered cylindrical shape wherein the inlet is widerthan the bottom and a height of about 10,000 to 17,000 Å.

Upon the lower electrode 128, as shown in FIGS. 1A to 1E, a layer ofHfO₂ may then be deposited by an ALD process using hafnium alkoxideprecursors such as Hf(OtBu)₄ and an activated oxidant such as O₃, plasmaO₂, remote plasma O₂ or plasma N₂O, to form dielectric layer 130 of thecapacitor. As described above, an ALD process using hafnium alkoxideprecursors and an activated oxidant is utilized to obtain the dielectriclayer 130 having an excellent step coverage in which the ratio of anupper thickness (t1) to a lower thickness (t2) is no less than 1:0.8 ona lower electrode 128 having an aspect ratio of 13:1 or more. Thedielectric layer 130 may be formed from a single layer of HfO₂ or may bea composite layer of two or more metal oxides deposited sequentially.For example, Hf and Al metal precursors utilized in the exemplary ALDprocess may be alternated to form a dielectric layer 130 having astacked structure consisting of alternating Al₂O₃ and HfO₂ layers. Thenumber and relative thickness of the layers in such heterogeneousdielectric layers may be adapted as desired to obtain a variety ofdielectric films.

If the lower electrode 128 is formed from polysilicon, oxygen (O)separated from the oxidant may react with the silicon of the lowerelectrode 128 during the formation of the dielectric layer 130, therebyresulting in some oxidation of the lower electrode 128. Accordingly,before forming the dielectric layer 130 on a polysilicon electrode, arapid thermal nitridation may be carried out in an atmosphere containingN₂ gas or ammonia to nitrify the surface of the lower electrode 128,thereby preventing or reducing the reaction of the oxidant used to formthe dielectric layer 130 with the lower electrode 128.

Referring to FIG. 6D, after completing the formation of the dielectriclayer 130 by the ALD process using metal alkoxide precursors and anozone oxidant, the dielectric layer 130 may be annealed in an oxidizingatmosphere such as UV-O₃, to reduce or eliminate contaminants and cureoxygen defects.

An upper electrode 132 of the capacitor is deposited on the dielectriclayer 130 to form the capacitor (C) including the lower electrode 128,the dielectric layer 130 and the upper electrode 132. The upperelectrode 130 may comprise a semiconductor material such as polysilicon,noble metals including Ru, Pt, Ir or a combination thereof, or aconductive metal nitride including TiN, TaN, WN or a combinationthereof. In an exemplary embodiment, the upper electrode 132 is formedas a stacked structure of TiN/polysilicon.

FIG. 7 is a graph showing a leakage current of the capacitor having adielectric layer formed by the ALD process in accordance with anexemplary embodiment of the present invention. In the graph, thehorizontal axis represents an applied voltage (V) and the vertical axisrepresents the measured leakage current (A/cell).

The capacitor was formed through the method shown in FIGS. 6A to 6E.Specifically, the surface of the lower electrode consisting of P-dopedpolysilicon was nitrified by rapid thermal process (RTP) using NH₃ gas.An exemplary ALD process using Hf(OtBu)₄ and O₃ was then used to form afirst HfO₂ film to a thickness of about 20 Å that was annealed usingUV-O₃. A second ALD HfO₂ film of about 50 Å was then deposited on thefirst ALD HfO₂ film using Hf(OtBu)₄ and O₃, followed by a second annealusing UV-O₃ to produce a HfO₂ film consisting of two atomic layers. ATiN film was then deposited on the HfO₂ film using TiCl₄ and NH₃ sourcegases and a P-doped polysilicon film was, in turn, deposited on the TiNfilm to form an upper electrode consisting having a TiN/polysiliconstacked structure.

As shown in FIG. 7, the capacitor manufactured according to exemplaryembodiments of the present invention exhibits a leakage current of lessthan 1 fA/cell at 1V. Accordingly, capacitors utilizing a HfO₂dielectric layer manufactured in accord with the exemplary embodimentsof the present invention exhibits improved electric characteristicsincluding a more stable leakage current, even when deposited on aelectrode structure having an aspect ratio of 13:1 or more.

Second Exemplary Method of Manufacturing a Semiconductor Device

FIG. 8 is a cross-sectional view of a cylindrical capacitor inaccordance with another exemplary embodiment of the present invention.Although as described in connection with this exemplary embodiment, thecapacitor is cylindrical, it should be appreciated that the capacitorelectrodes may be formed in a wide range of geometries.

Referring to FIG. 8, the cylindrical capacitor has a structure in whicha TEOS layer 200 is patterned and etched to form a cylindrical shape ona semiconductor substrate (not shown). A lower electrode 210, a Ta₂O₅dielectric layer 220 and an upper electrode 230, which then sequentiallystacked along the TEOS layer 200. The lower electrode 210 and the upperelectrode 230 may be comprise polysilicon, a noble metal such as Ru, Pt,Ir or a combination thereof, or a conductive metal nitride such as TiN,TaN, WN or a combination thereof. In addition to embodiments utilizing asingle metal nitride layer, a solid solution nitride layer such as (Ti,Ta)N can be used as the upper electrode, along with other materials.Similarly, a composite electrode formed by depositing or otherwiseforming layers of at least two of the noted conductive materialsdescribed above can be used.

In exemplary embodiments of the present invention, the Ta₂O₅ layer isdeposited using tantalum precursors of a monomer expressed by Formula IIand ozone gas as source gases.

As shown in Formula II, X has a coordinate bond with Ta formed throughan unshared electron pair. In an exemplary embodiment, X may be N, S, O,or C═O and R₁ and R₂ may be independently selected alkyl groups such asa C₁ to C₄ alkyl group. In an exemplary embodiment, R₁ and R₂ are methylgroups.

In an exemplary embodiment, ozone gas is used as an oxygen source fordepositing the Ta₂O₅ layer. The O₃ gas can be used as an oxidizer forforming a Ta₂O₅ layer at a temperature below 400° C., in contrast to thethermal conditions employed using O₂, H₂O or N₂O. It should beappreciated that other temperature conditions can be employed.

The Ta₂O₅ layer can be formed by thermal chemical vapor deposition (CVD)or atomic layer deposition (ALD) techniques, as well as othertechniques. According to the thermal CVD method, tantalum precursors andozone gas simultaneously flow into a deposition chamber. Conversely,tantalum precursors and ozone gas sequentially flow into a depositionchamber to deposit a Ta₂O₅ layer using an ALD method.

One example of an ALD method of forming a Ta₂O₅ layer in accordance withexemplary embodiments the present invention may be carried out asfollows. It should be appreciated that variations from this method canoccur with departing from the scope of the invention.

A semiconductor substrate on which a lower electrode 210 is formed isintroduced into a deposition chamber. A flow of 1-2000 sccm of a firstreactant including a first atom, i.e., tantalum (Ta), for forming thedesired thin film and at least one alkoxide group, i.e., tantalumprecursors expressed by Formula II, is introduced into the chamber sothat the first reactant is chemically or physically absorbed on thesurface of an Ru electrode 210 of the semiconductor substrate. Thetantalum precursors are typically provided by a bubbling method or aliquid delivery system (LDS) method.

After the adsorption is completed and a desired time has elapsed, a flowof 1-2000 sccm of an inert purge gas such as argon or nitrogen isintroduced into the chamber to remove the remaining tantalum precursorsfrom the chamber, while the adsorbed tantalum precursors remain in thechamber.

After the purge is completed, the inflow of the purge gas is stopped anda flow of 1-2000 sccm of a second reactant, i.e., ozone gas, isintroduced into the chamber. The ozone gas then reacts with the adsorbedtantalum precursors to form a Ta₂O₅ layer. After the inside of thedeposition chamber is again purged with an inert gas such as argon ornitrogen, a cycle of: (1) inflow of tantalum precursors, (2) inflow ofpurge gas, (3) inflow of ozone gas, and (4) inflow of purge gas may becarried out repeatedly to form a Ta₂O₅ layer 220 having a desiredthickness.

During the deposition, the temperature of the chamber may range fromabout 100° C. to about 600° C., and the pressure of the chamber mayrange from about 0.1 Torr to about 30 Torr.

After the formation of the lower electrode 210 and before the formationof the Ta₂O₅ layer 220, a process for forming a tantalum preprocessedlayer (not shown) can be additionally performed by repeating the inflowand purging of the tantalum precursors expressed by Formula II. Thissequence can result in the simplification of the formation of the Ta₂O₅layer. In such an exemplary embodiment, a thin Ta₂O₅ layer is formed onthe lower electrode with the tantalum precursors. Due to the presence ofthe Ta₂O₅ layer, the oxidation of the lower electrode in an oxygenatmosphere may be reduced or prevented. Thus, a Ta₂O₅ layer havingsuperior step coverage may be obtained.

An upper electrode 230 is formed on the dielectric layer 220, thedielectric layer 220 being fabricated as set fourth above. The upperelectrode 230 can comprise polysilicon, a noble metal such as Ru, Pt, Iror a combination thereof, or a conductive metal nitride such as TiN,TaN, WN or a combination thereof. In addition to an employment of asingle metal nitride layer, a solid solution nitride layer such as (Ti,Ta)N can be used as the upper electrode, along with other materials.Also, a composite layer formed by depositing at least two of theconductive materials described above can be used.

Experiment 1

A tantalum dielectric layer was formed on a cylindrical Ru lowerelectrode having an aspect ratio of about 15:1 using tetraethoxytantalum dimethylamino-ethoxide (TAT-DMAE) as a tantalum precursor andO₃ gas as an oxygen source. The dielectric layer was formed by an ALDmethod having a cycle of inflow of tantalum precursors->purging->inflowof O₃ gas->purging. In this experiment, the temperature of the chamberwas maintained at temperatures of 250° C., 300° C., 350° C. and 400° C.The thickness of the upper portion of a Ta₂O₅ layer deposited at eachtemperature (t₁ of FIG. 8) and the thickness of the lower portion of theTa₂O₅ layer (t₂ of FIG. 8) were measured. The results of thesemeasurements are shown below in Table 1.

TABLE 1 Classification 250° C. 300° C. 350° C. 400° C. t1 (Å) 240 103233 244 t2 (Å) 220 102 207 228

As shown in Table 1, the thicknesses of the deposited layers vary withtemperature. Notwithstanding these differences, it was observed that theTa₂O₅ layer exhibited thickness uniformity of at least about 90% withrespect to the layer formed on upper portions and lower portions.

Comparative Example 1

For comparison with the present invention, a Ta₂O₅ layer was formed byALD method at a temperature of 350° C. using PET as the tantalumprecursor and O₂ and H₂O gases as the oxygen sources, respectively.

FIGS. 9A and 9B schematically illustrates sections of the substrate whenTa₂O₅ layers are formed using the above-mentioned oxygen sources.

When H₂O was employed as the oxygen source gas, the Ta₂O₅ layer 220 wasdeposited on the upper portion of the opening 240, but the Ta₂O₅ layer220 was not deposited on the lower portion of the opening 240. It isbelieved that the formation of the Ta₂O₅ layer 220 was prevented due tothe presence of RuO₂ 210′ formed by surface oxidation of the Ru layer210 under the opening 240.

As shown in FIG. 9B, when O₂ is employed as the oxygen source gas, noTa₂O₅ layer was deposited on the entire surface of the opening 240.

Comparative Example 2

Ta₂O₅ layers were formed by ALD method at temperatures of 250° C., 300°C., 350° C. and 400° C. using PET as tantalum precursor and O₃ as anoxygen source.

This example illustrates similar results to Comparative Example 1 thatemployed H₂O as the oxygen source gas. Referring to FIG. 9A, the Ta₂O₅layer 220 was deposited on the upper portion of the cylindrical opening240 at each temperature, but the Ta₂O₅ layer was not deposited on thelower portion of the opening 240. Further, as the deposition temperaturewas increased, the depth to which the Ta₂O₅ layer 220 was formed(designated as h in FIG. 9A) tended to increase. Table 2 illustrates thethicknesses (designated as t₁ and t₂ in FIG. 8) of the upper portion andlower portion of the Ta₂O₅ layer 220 formed at 300° C. and 350° C., andalso the depth to which the Ta₂O₅ layer 220 was formed (designated as hin FIG. 9A).

TABLE 2 Classification 300° C. 350° C. t1 (Å) 549 456 t2 (Å) ~0 ~0 H (Å)3300 6700

Although not intending to be bound by theory, one possible reason as towhy tantalum precursors of exemplary embodiments of the presentinvention expressed by Formula II display superior coverage to othertantalum precursors such as PET will be described with respect to sterichindrance believed to be attributable to equilibrium vapor pressure andsticking probability impacting the tantalum precursor molecularstructure.

FIG. 10 illustrates equilibrium vapor pressure with respect totemperatures of PET and TAT-DMAE. As reflected in FIG. 10, theequilibrium vapor pressure of TAT-DMAE is higher than that of PET.Therefore, at the same temperature, the equilibrium vapor pressure ofTAT-DMAE is generally higher than that of PET over a given temperaturerange. In accordance with exemplary embodiments of the presentinvention, since a tantalum precursor source gas is provided at 140° C.with respect to PET and at 120° C. with respect to TAT-DMAE, theequilibrium vapor pressure of TAT-DMAE is observed to be about twice asgreat as that of PET. A high equilibrium vapor pressure indicates thatthere are a greater number of gas molecules relative to a system havinga lower equilibrium vapor pressure. With respect to a TAT-DMAE system,the amount of tantalum source gas provided into the deposition chamberis sizeable. Accordingly, the number of molecules directly provided tothe lower portion of the cylindrical opening is believed to berelatively large. Therefore, TAT-DMAE employed as precursors inaccordance with exemplary embodiments of the present invention can forma Ta₂O₅ layer exhibiting superior coverage to the conventional PET.

Not intending to be bound by theory, it is believed that thediscrepancies in vapor pressures can be attributed to a steric effect.According to Bradley, “Metal Alkoxides as Precursors for Electronic andCeramic Materials” American Chemical Society, Chem. Rev., (1989), smallalkoxides have a greater tendency to form oligomers such as dimers,trimers, etc. by bridging alkoxide groups than alkoxides having greatersteric bulk. This discrepancy is believed to exert a sizeable influenceon alkoxide vapor pressure.

Accordingly, since an oxygen atom present in PET has a tendency toincrease its coordination number by forming a covalent bond with aneighboring tantalum atom, the PET is likely to have the followingmolecular structure in a liquid state (see Formula III).

Conversely, with respect to a TAT-DMAE embodiment, because a nitrogenatom, which has a covalent bond with oxygen, has a coordination bondwith a Ta atom, the TAT-DMAE exists as a monomer in a liquid state andcan be expressed by the following structural formula (see Formula IV).

Accordingly, it is believed that since PET has a higher thermalstability than the TAT-DMAE precursors utilized in the exemplaryembodiments of the present invention, the PET requires more energy tobreak a bond between molecules to be volatilized and thus has a lowervapor pressure.

Another factor that potentially influences precursor coverage relates tosticking probability. According to Kawahara, “Conformal Step Coverage of(Ba, Sr)TiO₃ Films Prepared by Liquid Source CVD UsingTi(t-BuO₂)₂(DPM)₂”, Japanese Journal of Applied Physics, Vol. 38, pp.2205-2209, when Ti(t-BuO₂)₂(DPM)₂ precursors are used, (Ba, Sr)TiO₃Films have superior step coverage relative to embodiments which employTi(DPM)₂ precursors. Because the sticking probability of theTi(t-BuO₂)₂(DPM)₂ referenced by Kawahara is estimated to be about 0.02,and the sticking probability of the Ti(DPM)₂ is estimated to be about0.1, a thin film having superior coverage can be obtained when thesticking probability is low.

According to Si-woo Lee et al., “Chemical Vapor Deposition Precursorsfor (Ba, Sr)TiO₃ Films”, 6^(th) Korean Semiconductor Seminar, thedeposition of Ti may be carried out using the surface reaction as a ratedetermining step, and high coverage may be achieved by virtue of thesurface movement of Ti.

In view of all potential factors, and although not intending to be boundby any particular theory, it is believed that Ti precursors possessinglow sticking probability are particularly suitable for forming thinfilms having a high degree of coverage, presumably due to relative easeof surface movement. With respect to precursor steric hindrance, sincegenerally bulky precursors have a higher sticking probability than smallprecursors, the TAT-DMAE precursors may have a lower stickingprobability than that of PET, and thus, this may explain the superiorstep coverage of TAT-DMAE.

FIG. 11 illustrates an adsorption mechanism of gaseous tantalumprecursors on an Ru lower electrode according to an exemplary embodimentof the present invention. As reflected in FIG. 11, the mechanism inwhich the tantalum precursors reach the lower portion of the opening 240formed by the Ru lower electrode 210 is believed to be attributable to:(a) surface movement 11 from the upper portion of the opening 240 or (b)direct transmission 12 to the lower portion of the opening 240.Accordingly, as shown in FIG. 9A or FIG. 10, in order to minimize orreduce oxidation of Ru in the lower portion of the Ru lower electrode210, the provided tantalum precursors may be uniformly adsorbed and maycover the entire lower electrode 210 by surface diffusion or directtransmission.

In order to carry out this procedure in optimal fashion, surfacemovement of the precursors adsorbed on the substrate may beunencumbered, and the vapor pressure should be sufficiently high toaccommodate a plurality of precursors. In particular, precursors such asTAT-DMAE according to exemplary embodiments of the present inventiontypically possess a higher vapor pressure and superior surface movementrelative to conventional precursors such as PET, thereby forming a Ta₂O₅layer exhibiting improved coverage.

Although the above exemplary embodiments illustrate HfO₂ films and Ta₂O₅film, it is apparent to any person skilled in the art to apply an ALDprocess according to the present invention to various metal oxides suchas ZrO₂, Nb₂O₅, Al₂O₃, TiO₂, CeO₂, In₂O₃ and RuO₂

In the case of Al₂O₃, aluminum alkoxide precursors such as Al[OC₂H₅]₃ orAl(OCH(CH₃)₂)₃ and an activated oxidant such as O₃, plasma O₂, remoteplasma O₂ or plasma N₂O may be used. A TiO₂ film may be deposited by ALDprocess using titanium alkoxide precursors such as Ti[OC₂H₅]₄ orTi(OCH(CH₃)₂)₄ and an activated oxidant. In the case of Nb₂O₅, a niobiumalkoxide precursor such as Nb[OC₂H₅]₅ may be used. In the case of ZrO₂,a zirconium alkoxide precursor such as Zr(OtBu)₄ may be used.

According to exemplary embodiments of the present invention as describedabove, a thin film is deposited by ALD process using one or more metalalkoxide precursors and one or more activated oxidants that contain nohydroxyl group. The thin film manufactured by exemplary embodiments ofthe present invention show improved dielectric characteristics includingreduced leakage current and improved step coverage.

Although the exemplary embodiments of the present invention have beendescribed, it is understood that the present invention should not belimited to these exemplary embodiments but various changes andmodifications can be made by one skilled in the art within the spiritand scope of the present invention as hereinafter claimed.

1. A method of forming a layer of material on a substrate surface usingatomic layer deposition (ALD) comprising the steps of: chemisorbing analkoxide vapor onto the substrate surface to form an alkoxide layer; andreacting the alkoxide layer with an activated oxidant that does notinclude a hydroxyl group to form the layer of material on the substratesurface.
 2. A method of forming a layer of material on a substratesurface according to claim 1, wherein the material is an insulatingmaterial.
 3. A method of forming a layer of material on a substratesurface according to claim 1, wherein the material is selected from agroup consisting of HfO₂, ZrO₂, Ta₂O₅, Y₂O₃, Nb₂O₅, TiO₂, CeO₂, In₂O₃,RuO₂, MgO, SrO, B₂O₃, SiO₂, GeO₂, SnO₂, PbO, PbO₂, V₂O₃, La₂O₃, As₂O₅,As₂O₃, Pr₂O₃, Sb₂O₃, Sb₂O₅, CaO and P₂O₅.
 4. A method of forming a layerof material on a substrate surface according to claim 1, wherein thealkoxide is a metal alkoxide or a semimetal alkoxide.
 5. A method offorming a layer of material on a substrate surface according to claim 4,wherein the alkoxide is at least one metal alkoxide selected from thegroup consisting of alkoxides of Ti, Zr, Hf, Ge, Sn and Pb.
 6. A methodof forming a layer of material on a substrate surface according to claim5, wherein the activated oxidant is at least one oxidant selected fromthe group consisting of O₃, plasma O₂, remote plasma O₂ and plasma N₂O.7. A method of forming a layer of material on a substrate surfaceaccording to claim 4, wherein the alkoxide includes a hafnium alkoxide.8. A method of forming a layer of material on a substrate surfaceaccording to claim 7, wherein the alkoxide includes at least onealkoxide selected from the group consisting of Hf(OEt)₄, Hf(OPr)₃,Hf(OBu)₄, Hf(OnBu)₄, Hf(OtBu)₄, Hf(mmp)₄, Hf(OtBu)₂(dmae)₂,Hf(OtBu)₂(mmp)₂ and Hf[OSi(C₂H₅)]₄.
 9. A method of forming a secondlayer of material on a substrate surface according to claim 1, furthercomprising: chemisorbing a second alkoxide vapor onto the layer ofmaterial on the substrate surface to form a second alkoxide layer; andreacting the second alkoxide layer with a second activated oxidant thatdoes not include a hydroxyl group to form the second layer of materialon the substrate surface.
 10. A method of forming a second layer ofmaterial on the substrate surface according to claim 9, wherein thealkoxide vapor and the second alkoxide vapor include the same alkoxide.11. A method of forming a second layer of material on the substratesurface according to claim 9, wherein the alkoxide vapor and the secondalkoxide vapor are metal alkoxides including different metals.
 12. Amethod of forming a layer of material on a substrate surface accordingto claim 1, wherein: chemisorbing the alkoxide vapor onto the substratesurface to form an alkoxide layer and reacting the alkoxide layer withthe activated oxidant to form the layer of material on the substratesurface are conducted at a temperature of between about 100° C. andabout 500° C.
 13. A method of forming a thin film using atomic layerdeposition (ALD) comprising, in order: (a) placing a substrate into achamber; (b) introducing a first reactant into the chamber, the firstreactant including an alkoxide; (c) chemisorbing a portion of the firstreactant onto the substrate to form an alkoxide layer; (d) removing anon-chemisorbed portion of the first reactant from the chamber; (e)introducing a second reactant into the chamber, the second reactantincluding an activated oxidant that does not contain a hydroxyl group;(f) chemically reacting a portion of the second reactant with thealkoxide layer to form a thin film of oxide as an atomic layer on thesubstrate; and (g) removing a non-reacted portion of the second reactantfrom the chamber.
 14. A method of forming a thin film using atomic layerdeposition (ALD) according to claim 13, wherein the first reactantincludes a hafnium alkoxide.
 15. A method of forming a thin film usingatomic layer deposition (ALD) according to claim 14, wherein the firstreactant is at least one hafnium oxide selected from the groupconsisting of Hf(OEt)₄, Hf(OPr)₃, Hf(OBu)₄, Hf(OnBu)₄, Hf(OtBu)₄,Hf(mmp)₄, Hf(OtBu)₂(dmae)₂, Hf(OtBu)₂(mmp)₂ and Hf[OSi(C₂H₅)]₄.
 16. Amethod of forming a thin film using atomic layer deposition (ALD)according to claim 13, wherein the second reactant is at least oneoxidant selected from the group consisting of O₃, plasma O₂, remoteplasma O₂ and plasma N₂O.
 17. A method of forming a thin film usingatomic layer deposition (ALD) according to claim 13, wherein the steps(b) to (g) are repeated at least once to increase a thickness of thethin film formed on the substrate.
 18. A method of forming a thin filmusing atomic layer deposition (ALD) according to claim 13, wherein thesteps (b) to (f) are conducted at a temperature in a range between about100° C. to about 500° C.